1. Field of the Invention
The present invention relates generally to the field of medical catheters. More specifically, the present invention relates to recovery catheters used in distal embolic protection.
2. Description of the Related Art
Medical catheters are commonly employed for use in a lumen of a patient's body. The catheter enters the patient's body at an access site and is advanced through the lumen to a treatment site. The lumen may be in the patient's vascular system, such as that in a blood vessel, and the treatment site may be a stenosed region where a portion of the lumen is narrowed due to build-up of material on the lumen wall. Such narrowing is known as a stenosis.
The catheter may be guided to the treatment site through utilization of a guidewire. The guidewire typically is an elongated member having a distal end and a proximal end. The guidewire enters the patient's body at the access site and is advanced through the lumen to the treatment site. The distal end of the guidewire is the end nearest the treatment site, whereas the proximal end is the end nearest the access site. The guidewire may be positioned in proximity to the treatment site such that the distal end of the guidewire is moved to the proximal side of the treatment site (i.e., the side of the treatment site nearest the access site). The distal end of the guidewire may then cross the treatment site, thereby positioning the distal end of the guidewire on the distal side of the treatment site (i.e., the side of the treatment site farthest from the access site).
Generally, catheters comprise an elongated tubular body having a central lumen in which a guidewire can be received. The catheter is advanced along the guidewire for positioning at the treatment site. The catheter has a distal end that is advanced through the lumen of the patient's body to the treatment site.
The catheter body may have a diameter that makes it particularly difficult to advance the catheter across the treatment site if a stenosis has significantly narrowed the lumen. The prior art addresses this problem by providing a distal tip of the catheter which is tapered radially inwardly in the distal direction. Such a tapered distal tip allows for the catheter to be advanced through a narrowed portion of the lumen.
Another problem that may occur is that the catheter can become caught on a stent. A stent, generally, is a tubular wire structure that is positioned within a stenosis to maintain the lumen diameter. When a catheter is advanced across an area having a stent, the distal tip may engage an edge of the stent which can prevent further advancement of the catheter. Catheter advancement past a stent can be especially problematic when the stent is implanted in a curved vessel, or when the stent is underexpanded or incompletely deployed. This problem has been addressed by the prior art by rounding the distal tip or tapering the distal tip down to the approximate outer diameter of the guidewire in order to minimize the surface area available for engagement of the stent. This approach also provides for a gradual transition from the wire diameter to the catheter outer diameter, and tends to center the catheter in relation to the stent to facilitate stent crossing.
Some devices, such as embolic protection devices, may have a host wire that acts as a guidewire for other devices including catheters. An embolic protection device is a collapsible/expandable filter affixed to the distal portion of a guidewire. In the collapsed state, the embolic protection device is compressed toward the guidewire to give the device a smaller diameter so that it can be advanced within the lumen. In the expanded state the embolic protection device deploys outwardly from the guidewire such that it engages the wall of the lumen and acts as a filter by allowing fluid, such as blood, to pass therethrough while preventing emboli or particulate matter entrained in the fluid from passing therethrough. Emboli or particulate matter may become entrained in the fluid when a stenosis is being treated. Such particles of the stenosis may become dislodged due to contact with a treatment apparatus. Such treatments may include ablation procedures such as thrombectomy and atherectomy procedures, balloon angioplasty, stenting, and the like.
After treatment, the embolic protection device is typically collapsed in a manner wherein it maintains the captured emboli as the device is removed from the lumen. To prevent the release of the emboli back into the fluid, it is preferred to enclose the embolic protection device within a catheter. The collapsed embolic protection device has a proximal periphery that is greater than that of the outer diameter of the guidewire. Prior art catheters for receiving an embolic protection device have a relatively large diameter so as to receive the captured emboli containing protection device. Such catheters can be difficult to advance through a narrowed portion of a vessel or may become caught on a stent. If such catheters are provided with tapered tips, as described above, it becomes difficult to receive an emboli filled protection device within the catheter due to the small diameter of the tapered catheter tip. Alternatively, if prior art catheters are made small in diameter to facilitate stent crossing, it is possible that captured embolic material will be extruded through the distalmost part of the protection device filter during withdrawal of the emboli filled protection device into the small diameter catheter.
It would be advantageous to provide a catheter having a distal tip that allows passage of the catheter through a narrowed or stented portion of a lumen, while being able to receive an embolic protection device therein.